1. Field of the Invention
The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus which images a large screen using a plurality of two-dimensional image sensors which are discretely arranged.
2. Description of the Related Art
Recently in the pathology field, a virtual slide apparatus is attracting attention, which images a sample placed on a preparation, and digitizes the image, so as to make a pathological diagnosis on the display possible. By digitizing the image for pathological diagnosis by a virtual slide apparatus, the optical microscopic image of the sample on the preparation can be handled as digital data. The expected merits of this are a quick remote diagnosis, a description of diagnosis to a patient using digital images, the sharing of rare cases, and making education and practical training efficient.
In order to digitize the operation in the optical microscope using the virtual slide apparatus, the entire sample on the preparation must be digitized. By digitizing the entire sample, the digital data created by the virtual slide apparatus can be observed by viewer software, which runs on a PC and WS. Image sensors are used to digitize an optical image. In the case of corresponding 0.5 μm on the sample to one pixel of the image sensor, 900,000,000 pixels (30,000 pixels×30,000 pixels) are required to digitize the entire sample if the size of the sample on the preparation is 15 mm×15 mm. The size of an effective light receiving area demanded for the image sensor is 90 mm×90 mm if the magnification of an objective lens is 6 times, or is 120 mm×120 mm if the magnification is 8 times. A single unit two-dimensional multi-pixel large size image sensor that can implement this requirement has high cost. Therefore in a virtual slide apparatus, an area of the sample is normally divided into a plurality of areas, and imaged using a two-dimensional image sensor having several hundred thousand to several million pixels, or a one-dimensional image sensor having several thousand pixels.
The tiling method using one two-dimensional image sensor captures images of a test sample for a plurality of times while moving the two-dimensional image sensor relative to the test sample, and acquires the entire image of the test sample by pasting the plurality of captured images together without openings. A problem of the tiling method using a single two-dimensional image sensor is that it takes more time in capturing images as a number of divided areas increases in the sample.
As a technology to solve this problem, the following technology has been proposed (see Japanese Patent Application Laid-Open No. 2009-003016). Japanese Patent Application Laid-Open No. 2009-003016 discloses a technology which includes an image sensor group comprised of a plurality of two-dimensional image sensors disposed within the field of view of an objective lens, and images an entire screen by capturing the images a plurality of number of times while relatively changing the positions of the image sensor group and the position of the sample. Thereby the imaging time is decreased. Furthermore, the moving mechanism is simplified and the moving time is decreased by limiting the direction of the relative change between the position of the image sensor group and the position of the sample to a uniaxial direction.
In Japanese Patent Application Laid-Open No. 2009-003016, the restrictions in the arrangement using a plurality of two-dimensional image sensors is not referred to. Actually because of such restrictions as the silicon wafer size, the package size, the interference between packages, the sensor holding substrate and the sensor holding mechanism, the two-dimensional image sensors must be arranged with a dead zone there between. Particularly in the case of a two-dimensional image sensor up to several million pixels, a ratio of the dead zone, other than a light receiving area, with respect to the light receiving area, is high, and the influence of the restrictions is major. In the case of restricting the relative change of the positions of the image sensor group and the position of the sample to the uniaxial direction, and in the case of considering the above mentioned dead zone and the imaging target area being square (or a form close to square), the number of times of moving tends to increase and imaging takes time.
The moving mechanism can be simplified if the moving mechanism is disposed not at the two-dimensional image sensor group side, but at the preparation side, because the moving distance can be decreased since the optical magnification causes no influence. In the case of Japanese Patent Application Laid-Open No. 2009-003016, the two-dimensional image sensors are disposed outside the imaging target area image, hence the effective field of view of the imaging optical system must be increased if the moving mechanism is disposed at the preparation side, which leads to an increase in the size of the imaging optical system and an increase in cost.